A Sanskrit music scholar in 13th century India worked out how to recover a particular arrangement of notes from its number in a list. Centuries later, Donald Knuth recognised the computer science in work like this. Yes, the Donald Knuth who wrote The Art of Computer Programming.... In an ACM interview, he recalled reading translations of 13th-century Sanskrit works and said some of those Indian musicians "would have been computer scientists if they were living today." His written history of combinatorics points to Sharngadeva's Sangitaratnakara, a Sanskrit treatise on music. The problem sounds musical: how do you systematically list the possible orderings of a set of notes? But the text goes further. Given an arrangement, find its position in the list. Given the position, reconstruct the arrangement. That second operation is worth pausing over. You have the number of an entry, but not the entry itself. How do you recover it without first writing out everything that comes before it? The methods use a representation based on factorials, with a table supporting the conversion. These operations are now called ranking and unranking: moving from an arrangement to its numerical address, and back again. This was not a Sanskrit verse that vaguely resembled a modern idea. It was a procedure for solving a precise problem, preserved in a music text. Knuth's interview does not name Sharngadeva. His separate written account does. There is no need to stretch that into a claim that modern computers copied the text. The remarkable part is already there: a medieval Indian music scholar working through the mathematics of finding one arrangement among many, in both directions. Sources: Sharngadeva, Sangitaratnakara, 1.4.60-71; Donald E. Knuth, "Two thousand years of combinatorics", Combinatorics: Ancient and Modern, OUP (2013); Knuth, ACM ByteCast, Episode 2; M. D. Srinivas, "Combinatorial Methods in Indian Music: Pratyayas in Sangitaratnakara of Sarngadeva". Photo 1 : Donald Knuth. Photo 2: His actual interview words about the Indian musicians who "would have been computer scientists if they were living today", highlighted in yellow. Photo 3: The key attribution page: Knuth explicitly names Sharngadeva's Sangitaratnakara and credits its earlier ranking/unranking algorithms and factorial representation. Photo 4: The technical explanation, highlighted: permutations of musical phrases, factorial representation, and the table for converting between a number and its representation.